Like most American schoolchildren, I studied the civil rights movement. Years later, I only remembered the highlights: Dr. Martin Luther King's "I Have a Dream" speech, the bus boycotts and the images of police dogs and water cannons being used on demonstrators.

But in researching this story, I learned that the real ground battle was being fought by ordinary African-Americans in small towns all over the South. They tried to vote and stood up to local Klan leaders and many, like Louis Allen, paid for it with their lives.

Most people have never heard of Louis Allen; certainly no one on our "60 Minutes" team knew who he was. But in reporting this story, we learned that his murder had a huge impact on the struggle for civil rights as a catalyst for Freedom Summer, which focused the nation's attention on the South.

But for nearly half a century, Louis Allen's murder case, and others like it, have become dormant and cold. On this week's Overtime segment, we give you a look at how, over the course of 18 months, we reported on this story.

And as Hank Allen, Louis' son, said to us: justice delayed is justice denied. If you have any information about this case, please contact us at 60m@cbsnews.com.